Cups made of paper material and comprising a peripheral deforming entity on the tubular wall are known in the prior art. Such deforming entities are provided, for example, for improving the stacking properties and the feel of such cups or also for maintaining a distance between an outer sleeve and a tubular wall so that an insulating space between the outer sleeve and the tubular wall is not compressed even when a full cup is held in the hand.
A generic cup is disclosed in European Patent EP 1 227 042. The aforementioned document describes a heat-insulating cup formed by two conical walls, the inner wall comprising an inwardly oriented groove that serves for stacking a cup of a similar type inside another cup in the stack. The inwardly oriented groove produced by a roll-in process is intended to impart effective stacking and unstacking properties to the cup without the possibility of a plurality of stacked cups becoming jammed inside each other. Experience has shown that the disclosed cup exhibits satisfactory properties that enable up to approximately 20 cups to be stacked. If substantially more cups are stacked, they become jammed inside each other. In particular, such cases of the stacked cups becoming jammed inside each other are caused by axial pressure that is directed from the open end of the cup to the bottom wall thereof as a result of the dead weight of the cups when a large number of cups are stacked together. The cups can become jammed inside each other even when a stack of 50 packed cups is put down with moderate force. Insufficient rigidity of the groove must be considered as the cause of the cups becoming jammed inside each other, but this insufficient rigidity cannot be improved on with this fabrication method, since the roll-in process to produce the groove reduces the strength of the material.
A cup having improved stacking properties over that mentioned above is described in German patent application DE 10 2004056932 A1, but this application again does not propose a satisfactory solution to the problem of the cups becoming jammed inside each other due to deformation of the tubular wall of the cup in the region of the peripheral deforming entity.